Method of printing through cellular plates



Feb 7, 1951 A. MURRAY mum: OF PRINTING moucu CELLULAR PLATES 2 Sheets-Sheet 1 Filed May 21, 1947 FIG. 5.

ALEJQINDER MURRAY I NVEN TOR ATTORNEY 0 AGENT -Feb."7, 1951 A. MURRAY METHOD OF PRINTING THROUGH CELLULAR PLATES 2 Sheets-Sheet 2 Filed May 21, 1947 ALEXANDER MURRAY INVENTOR BY WW ATTORNEY AGENT Patented Feb. 2?, 1951 METHOD OF PRINTING THROUGH CELLULAR PLATES Alexander Murray, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application May 21, 1947, Serial No. 749,447

3 Claims.

This invention relates to a method of printing and particularly to an improved manner of using a cellular printing plate or so-called Glassey Block as described by C. Q. Glassey, in his patent application Serial Number 745,019. filed April 30, 1947.

The object of the present invention is to provide greater speed of operation and greater simplicity in the use of the Glassey Block, particularly the form of block which is inked from the rear.

The most important feature of the present invention is the fact that the printing fluid itself is used as the temperature control medium. In the Glassey printing system the plate is heated differentially in accordance with a radiant ener y image during each printing cycle and preferably should be returned to a standard initial temperature at the start of each cycle. According to the present invention, this is accomplished by controlling the temperature of the ink supply and by flowing a quantity of ink across the plate during the inking operation. Of course, the ink transferred from the front surface of the printing plate to the paper carries some of the heat with it so that at the end of the printing cycle the temperature of the plate is not as high as it would otherwise be. However, it is still somewhat above the initial temperature and therefore must be cooled.

The proper initial temperature and the range of temperature through which the plate or parts thereof may move depends on the particular printing fluid used and on the size of the cells. In general it appears better to have the initial temperature considerably above ordinary room temperature and for the sake of rapidity of operation, to have the maximum increment of temperature required to print as small as will conveniently deposit the required amount of ink.

The circulating ink should preferably be at an average pressure somewhat below atmospheric pressure so that there is a tendency to push ink from the front surface of the plate toward the rear, which tendency is overcome by the capillary action or surface tension at the narrow front openings of the cells in the Glassey block. This low pressure inking is applicable to all rear inking embodiments of the Glassey printing system.

The operation of the invention will be fully understood from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 is a greatly enlarged cross section of one form of cellular printing plate at the start of a printing cycle.

Figs. 2 and 3 illustrate slightly different forms of cells useful in such plates.

Fig. 4 is a perspective view partly cut away of apparatus for one embodiment of the present invention.

Figs. 5 and 6 are respectively a vertical section and a top view of a printing press incorporating another embodiment of the invention.

Fig. 7 is a vertical section of the essential parts of a four color printing press according to the 1 invention.

Fig. 8 similarly illustrates auxiliary parts of the printing press shown in Fig. 7.

In Fig. 1 a cellular plate i0 of metal or plastic or any other suitable material comprises a plurality of cells II more or less uniformly dis tributed over the area of the plate. There should be at least 1000 cells per square inch for 33 line quality and there should be 40,000 cells per square inch for 200 line quality. The cells have a narrow opening l3 through the front of the printing plate and preferably have a section 52 of reduced diameter joining this capillary opening l3 to the main part of the cell ll. Each of the cells is wide open to the rear of the plate. In fact over the rear surface, there is in general more cell area than wall structure, but this is not a critical feature of the invention.

In printing with such a plate, the cells are filled with ink, in a manner to be described in detail below, and then the rear opening of the cell is closed off by a transparent plate l4 clamped tightly on the plate. A negative [5 of the image to be printed is held against the plate [4 and illuminated from the above with light indicated by arrows 16. Alternatively the radiant energy image may be projected by a suitable lens system onto the plate Hi. In either case the radiant energy heats the ink in the cells I! and expels it through the orifices l3, differentially in accordance with the density of the negative l5, to form an image on a sheet of paper printing plate by a I], held in contact with the resilient layer l8.

For maximum speed of operation the idealcell is shown in Fig. 2 in which the capillary"oriflce 20 whose diameter is .0004 inch say, is of very short length so as to impose the minimum of the preferred form shown in Fig. 2.

The present invention is concerned with the method of inking and particularly the method of cooling the cellular printing plate between prints. One method according to the invention is illustrated in Fig.4 in which the printing plate 25 is set into and forms the major portion of the bottom of a relatively heavy metal box 25. The transparent cover sheet 21 for the cellular block is shown in the separated position. It is carried by a large glass block 13 and for contact printing, the negative is held between the plates 21 and 25. A rubber gasket 23 seals the join between the glass block 25 and a shelf 32 which together with the walls of the box -25 forms an ink chamber. Ink is supplied to this chamber and maintained at constant pressure therein by a pipe 30 and reservoir 3|. The reservoir 3| is shown open to the atmosphere but may be a closed chamber with controlled pressure for embodiments of the invention in which this pressure is maintained below atmospheric.

After each printing operation the transparent layers 21 and 28 are raised from the printing block 25 allowing the ink in the surrounding chamber to flow in across the back of the printing block 25. This ink is at a relatively low temperature due to the metal box 25 which may be kept cool by suitable fan or water circulating system not shown. This cooled ink tends to bring the temperature of the printing plate 25 back to its initial temperature. Thus the printing plate 25 is inked and cooled at the same time merely by the raising of the layers 21 and 28 away from the printing plate 25.

In Fig. the celludar printing plate 35 is carried in a supporting frame 35 and is shown between printing steps slightly above a layg 31 of paper to be printed. The rear layer 34 of the plate is also separated from the cells and as before a negative 39 is clamped between the layer 38 and a glass block 40 held by pegs 5| in place in a supporting frame 45. The frames 35 and 45 form a closed ink chamber sealed off by a seal 45 which allows the frame 45 to be raised from the frame 35 lifting the plate 38 from the back of the printing plate 35. This leaves a low chamber 4| immediately above the printing plate 35 across which cool ink is flowed as indicated by arrows 42. The ink is supplied through a pipe 43 and flows out through a pipe 44. The pumping mechanism 52, the cooling mechanism 53 and the means 59 for maintaining the desired pressure in the system are all shown in Fig. 6. The relatively cool ink brings the plate 35 to the proper starting temperature and then by'means of cams 48 and 49 carried on a cam shaft 41, the frame 45 is first moved down to bring the plate 38 in contact with the printing plate 35 closing off the ink cells and then the whole rinting system including frames 45 and 35 move down to bring the printing plate in contact with the paper 31.

It is sometimes desirable to work at slightly higher pressures in the ink circulating systems and these pressures occasionally allow ink to flow from the front surface of the printing plate before the printing operation starts, particularly as the plate 38 is moved into contact with the printing plate 35. In these embodiments, a doctor blade 55 is moved very rapidly across the front surface of the printing plate 35 by a driving mechanism 58 shown schematically, just before the printing plate 35 is moved into contact with I 3 I in length of capillary is not as critical as it is with the paper 31. It is preferable to have two sets of cams for raising and lowering the frames 35 and against a spring action (the showing of which has been omitted for the sake of clarity). The two sets of cams are driven by a single drive chain 55 operated by any suitable mechanism such as a motor 51.

The arrangement shown in Figs. '7 and 8 illustrates one form of four color printing press incorporating an embodiment of the invention very similar to that shown in Figs. 5 and 6. This particular press prints two colors on each side of a transparent pellicle which is later laminated to an opaque white support such as paper, but the present invention is applicable directly to other four color printing systems merely by registering the successive color separations made with arrangements such as shown in Figs. 5 and 6. In Figs. '1 and 8 a transparent pellicle 55 from a stock roll 55 is moved between two pairs of printing plates 53 for simultaneously printing two colors on each side of the pellicle. The pellicle moves from the printing box 85 across an illuminator 81 for inspection. The whole printing press, including motors and driving mechanisms is housed in a cabinet forming about a 30 inch cube for printing prints up to 8 x 10 inches. For clarity in Fig. 8 only the printing plates 53 are shown, but of course each is accompanied by a transparent closure plate and color separation negative 5| carried in a frame 52. In the position shown in Fig. 7, the rear plate is held away from the printing plate 53 by springs 59 leaving an ink chamber 54 through which ink is flowed by a pumping mechanism 15. The pumps 15. 15, etc. for the four plates are all carried on a single drive shaft 11. The pumps are shown by broken lines so as not to confuse the drawing which primarily illustrates the printing plates. The ink moves through pipes 18 and 19 and a cooling chamber 50 as above described in connection with Figs. 5 and 6. After the plates have been inked, the turning of the cam shaft 12 turns the cam 13 so that the plates 50 clamp the printing plate 53 sealing off the ink cells. The cams 14 then start to move the plate supporting frame 82 and the cams 13 continue to move the frames 52 so that contact betweenthe plates 50 and 53 is maintained. This clamps the pellicle 58 and then the light from lamps 85 illuminates the rear of each of the printing plates expelling ink to print on the pellicle as above described. The light is then cut oil! and the pellicle unclamped and moved to the next printing position in which the image printed by the cyan and purple printing plates 53 and is movedinto exact register with that to be printed by the yellow and magenta plates. When operating under conditions in which there is sufficient time and pressure on the ink to allow it to flow through the printing plate during the inking operation, doctor blades 8| are moved in front of the plates to the center of the printing system while the pellicle is moved forward and then just after the plate 55 is clamped to the plate 53 these doctor blades 5| wipe the printing plate surface very rapidly and move to the position shown in Fig. 7 where they remain during successive parts of the cycle. The operation of the cams 14 is against the force of springs 15 carried by the main frame 1| of the printing press.

Having thus described preferred embodiments 75 o! my invention. I wish to point out that it is large rear openings, closing the rear openings with a transparent sheet and heating the fluid in the cells by illuminating the rear surface with a radiant energy image absorbable by the fluid, said image being negative to that to be printed, to expel printing fluid from the narrow front openings, differentially in accordance with the image, onto a surface to be printed characterized by the step of re-inking the plate before each printing operation by raising the transparent sheet from the rear surface and flowing onto the rear surface, the printing fluid at a constant temperature just slightly below that at which the plate should be at the start of the illuminating step, the slight difference being just that which brings the plate to the starting temperature from the higher temperature it reaches at the end of the illuminating step,

2. The method according to claim 1 in which the printing fluid is circulated through a temperature control chamber and across the rear surface of the printing plate at an average pressure below the atmospheric pressure at the front surface of the plate, but not sufliciently below to overcome the surface tension which tends to hold the printing fluid level with the narrow front openings in the plate.

3. The method of printing through a cellular plate having cells uniformly distributed over the plate with a narrow opening of capillary dimensions from each cell through the front surface of the plate and a relatively large opening from each cell through the rear surface, by filling the cells with printing fluid through the relatively large rear openings, closing the rear openings with a transparent sheet and heating the fiuid in the cells by illuminating the rear surface with a radiant energy image absorbable by the fluid, said image being negative to that to be printed, to expel printing fluid from the narrow front openings, differentially in accordance with the image, onto a surface to be printed characterized by the step of re-inking the plate before each printing operation by raising the transparent sheet from the rear surface and flowing onto the rear surface, the printing fluid at an average pressure below the atmospheric pressure at the front surface of the plate, but not sufficiently below to overcome the surface tension which tends to hold the printing fluid level with the narrow front openings in the plate.

ALEXANDER MURRAY.

No references cited. 

3. THE METHOD OF PRINTING THROUGH A CELLULAR PLATE HAVING CELLS UNIFORMLY DISTRIBUTED OVER THE PLATE WITH A NARROW OPENING OF CAPILLARY DIMENSIONS FROM EACH CELL THROUGH THE FRONT SURFACE OF THE PLATE AND A RELATIVELY LARGE OPENING FROM EACH CELL THROUGH THE REAR SURFACE, BY FILLING CELLS WITH PRINTING FLUID THROUGH THE RELATIVELY LARGE REAR OPENINGS, CLOSING THE REAR OPENINGS WITH A TRANSPARENT SHEET AND HEATING THE FLUID IN THE CELLS BY ILLUMINATING THE REAR SURFACE WITH A RADIANT ENERGY IMAGE ABSORBABLE BY THE FLUID, SAID IMAGE BEING NEGATIVE TO THAT TO BE PRINTED, TO EXPEL PRINTING FLUID FROM THE NARROW FRONT OPENINGS, DIFFERENTIALLY IN ACCORDANCE WITH THE IMAGE, ONTO A SURFACE TO BE PRINTED CHARACTERIZED BY THE STEP OF RE-INKING THE PLATE BEFORE EACH PRINTING OPERATION BY RAISING THE TRANSPARENT SHEET FROM THE REAR SURFACE AND FLOWING ONTO THE REAR SURFACE, THE PRINTING FLUID AT AN AVERAGE PRESSURE BELOW THE ATMOSPHERIC PRESSURE AT THE FRONT SURFACE OF THE PLATE, BUT NOT SUFFICIENTLY BELOW TO OVERCOME THE SURFACE TENSION WHICH TENDS TO HOLD THE PRINTING FLUID LEVEL WITH THE NARROW FRONT OPENINGS IN THE PLATE. 